There are various switch monitoring circuits for monitoring a change in a state of a switch being currently used. For example, there are switch state monitoring circuits that monitor an ON/OFF state of a protection target switch.
Switch state monitoring circuits are configured to monitor an ON/OFF state of a monitoring target switch only when an ignition switch is ON. However, for example, a vehicle may separately have a battery and an ignition power source to supply power. In this case, there is a switch whose state is to be monitored even when the ignition switch is OFF. Thus, there is a demand for a switch state monitoring circuit that can appropriately select a monitoring target switch according to a state of the ignition switch.